In computer graphics, e.g., a non-realtime, physically based rendering, captured (e.g., High-Dynamic-Range (HDR) photographs) or rendered (e.g., a sky model) images are commonly used for backgrounds. These images can be used as an environment map, which serves as a wrap-around background image and a light source of a scene, and/or as a backplate, which serves as a fixed-perspective background image. These images are referred to as “background images.”
When background images are used to surround and light a scene, features in the background images look unconvincing as a virtual view point, e.g., camera position, of the scene deviates from the original position, i.e. the position at which the background was captured or generated. For example, when a position of a camera looking at the scene moves and shifts away from the original position, some of the features in the background images that are closer to the camera do not shift relative to those that are further away as they would in real life. Furthermore, all surfaces in the background image appear diffuse, e.g., reflection and refraction effects do not occur.
This is due to the fact that since the background images are 2-dimensional (2D) images, the only view point for correctly viewing the background images is the original position, and environment in the background images is at infinity by definition. Directional data for correctly illuminating the scene would only be available from the original position. Consequently, when projected into world-space, the background images become view-independent and lack parallax and would not be able to provide novel illumination information.
The above mentioned problems also occur when matte objects are used as a part of background images. Matte objects are placeholder geometry that is added as a stand-in for selected objects in the background images. They are used to simulate interactions between computer generated (“synthetic”) foreground objects and the background, such as foreground objects casting shadows onto a matte object or the reflections of foreground objects seen in a matte objects. As the appearance of matte objects is derived from the pixels of the background images, the matte objects also look diffuse and unconvincing and lack parallax when the view point differs from the original position. It is noted that the view point is always different from the original position when taking reflection and refraction into account.